I. Field of the Invention
This invention lies in the field of cataract surgery and in particular relates to the enzymatic treatment of cataracts followed by removal of the enzymatically digested cataractous material.
II. Background
The lens is an optically clear encapsulated disc-like structure which is suspended within the eye, behind the iris and in front of the vitreous. It supplies part of the optical refracting power of the eye. The lens becomes cataractous when it nuclear and/or cortical and/or subcapsular regions become opaque, thus blocking the path of light entering the eye, thereby causing diminished vision. A cataract is simply a lens that has become cloudy.
There are, generally speaking, two types of cataracts, congenital and senile. Congenital cataracts, approximately 1% of all cases, are found in people under the age of 25 and characteristically are relatively soft. Senile cataracts, approximately 99% of all cases, are found in older people and characteristically are relatively hard.
The Egyptians, who are believed to be the first to record treatment of cataracts, removed them by thrusting a rose thorn through the cornea and simple pushing the cataract back and down into the vitreous of the eye.
The next major procedure, one popular in the 1800's, took advantage of the fact that as a senile cataract develops it becomes more dense and cloudy, but after a number of years it becomes ripe, i.e. soft and liquid. The ripe or mature cataract was removed by making an incision in the eye near the cornea, cutting the anterior capsule and flushing the soft material out. It was not uncommon for the eye to become severely inflamed and, in addition, several operations were sometimes necessary to remove all lens debris. The greatest disadvantage of this procedure is that the patient could be blind for 10-20 years waiting for his or her cataract to become ripe.
The intracapsular technique of cataract surgery developed in the 1930's calls for making a large incision, 25 mm, approximately 180.degree. around the cornea for an entry into the anterior chamber of the eye. After breaking the suspensory ligaments which suspend the lens within the eye, the lens is removed by mechanical means such as forceps or suction. Removal of the lens may be facilitated by the use of alpha chymo-trypsin to dissolve the ligaments that attach the lens to the ciliary body (the zonules). The advantage of this technique is that a patient no longer has to wait years for the cataract to become ripe. Several disadvantages exist. The large incision in a relatively sensitive organ requires multiple stitches to close. The removal of any barrier holding the vitreous body in place makes physical activity impossible for several days after the operation since the vitreous can then become displaced. The sensitivity of the eye structure can result in significant damage to the iris, retina, etc. However, the intracapsular technique is the most common procedure practiced and it is estimated that heretofore well over 360,000 of such procedures have been carried out each year in the U.S. alone.
Another method of surgery currently practiced is applicable only to congenital cataracts. If the cataract is extremely soft and liquid, the surgeon enters the anterior chamber of the eye through a small incision, then breaks the lens capsule and aspirates the contents thereof out using a 18 gauge needle and a normal syringe. If the lens is a little too hard to be aspirated in this manner, the surgeon makes several incisions in the anterior capsule and allows the aqueous humour of the anterior chamber at attack and hydrolyze the cataract. After several days the lens becomes soft enough to allow the above mentioned aspiration technique to be employed. This procedure works only for soft congenital cataracts and is not effective for senile cataracts because of the hardness of the lens material. Also, the surgeon cannot cut open a senile cataract and then wait (a long period) for the natural enzymes to work since the eye soon becomes severely inflamed due to the reaction of the lens material with the vascularized areas of the eye.
The object of this invention is to provide a procedure which eliminates much, if not all, of the hazards and trauma involved in the above described and other known cataract surgical procedures.